Any mechanics around NW London?

[Kimmie]

Well, I asked some questions and this was the response....

I'm not totally sure what the problem is.
The car started running a little strangely a couple of months back, I took it to the garage and they replaced the alternator, but it didn't fix the problem, and it's got progressively worse.A light on the dash came up when it was struggling to start the other morning which is the 'Engine Auto Diagnostic Light'.
It's just parked outside my house, so I got a guy from Green Flag to come out and look at it, he said he thought one of the sensors had gone, but couldn't fix it. So I then got a mobile mechanic to look at it, and he seemed to think there may be something wrong with the Engine Management System but wasn't sure until he started working on it at a cost... And to be honest after just paying £400 on an alternator a couple of months back and also pay for this guys call out charge, I'm just going to cut my losses.
It might be something simple to fix, I'm not sure. Everything else was and has been working 100% fine until now.

Any insight to the problem from anyone?

It's a 6 btw